Pressure release tubes with rubber liners



March 10, 1970 G, A. VINCENT 3,

PRESSURE RELEASE TUBES WITH RUBBER LINERS Filed May 16, 1968 INVENTOR. ON A. VINCENT A TTOR/VE Y5 ates ABSTRACT OF THE DISCLOSURE The yieldable walls of metal or fiberglass tubes comprise the pressure release backing for a transducer vibrating diaphragm. To prevent collapse and destruction of the tubes at deep submergence, the tubes are each provided with a core for supporting the tube wall at the points where the walls would collapse and fracture.

BACKGROUND OF THE INVENTION A transducer operating in water is similar in many respects to a loudspeaker operating in air. The front surface of the vibrating diaphragm, or piston, must be isolated by a baflie from the rear surface of the diaphragm. Effective baflling is particularly necessary in water because of the high degree of coupling between the vibrating surfaces and the water. The motor element of the transducer is invariably housed within a watertight casing. The interior of the casing must be provided with pressure release material, the material being sufiiciently yieldable to accommodate the inward excursions of the piston. Note further that as depth of submergence increases the pressure on the outside of the transducer increases and there must be a compensating inside static pressure in the casing, else a depth and pressure would soon be reached at which the diaphragm would be effectively locked in one position. For this reason the interior of the casing must be vented to the external pressure. Heretofore, pressure release has been effected by elongated tubes of spring steel, aluminum, or fiberglass which when drawn and flattened in cross section have yieldable sides ideally suited for pressure release purposes. Unfortunately, the sides of the tubing completely collapse at extremely deep submergence and when the yield point of the material of the tube has been exceeded the pressure release properties are lost. Thereafter the transducer is inoperative.

The object of this invention is to provide a pressure release tube which will not fail at extreme hydrostatic pressures.

Other objects and features of this invention will become apparent to those skilled in the art by referring to the specific embodiments described in the following specification and shown in the accompanying drawing in which:

FIG. 1 shows a bundle of pressure release tubes constructed according to this invention;

FIG. 2 shows in perspective one of the pressure release tubes, partly in section;

FIG. 3 is a cross section, without external pressure, of one of the pressure release tubes of FIG. 1;

FIG. 4 is a cross section of the tube of FIG. 3, but with high or maximum external pressure; and

FIGS. 5 and 6 show the tube of FIG. 3 with different core members, before and after high external pressure.

The bundle 10 of pressure release tubes 12 may be of any desired length and may be stacked in any cross sectional configuration to fit within the transducer housing as desired. The particular transducer housing, not shown, intended for the bundle 10 is cylindrical in shape and is Patented Mar. 10, 1970 elongated. The walls of the transducer casing include several radiating elements. Hydrostatic pressure on the tubes 12 is the same as that of the exterior of the casing and is determined by the depth of submergence.

The characteristic of tubes 12 of importance here is that they will bend or yield to absorb the backwave of the radiating element and will be compliant at any hydrostatic pressure. While many materials respond to this condition fiberglass, aluminum, and stainless steel are found to be suitable. The tubes are each sealed, liquidtight, along the sides and at the ends. Plugs may be in serted in the ends of the tubes or, if desired, the ends of the tubes may be pinched together (not shown) and cemented or welded. Preferably, the bundle of tubes are joined to headers 8 at either end of the stack to hold them in position for assembly in the transducer casing.

It is to be reiterated that the pressure on tubes 10 can be extreme. At a depth of 10,000 feet, for example, the pressure will be greater than 4,000 lbs. per square inch. Naturally, it is desirable that the transducer be operable after it has been raised from such a depth. When the hydrostatic pressure is zero, the tube is flattened somewhat with the side walls 12a of the tube standing substantially parallel as shown in FIG. 3, and with the rounded edges 12b of the tube rolled or precast with the desired curvature. As the pressure is first applied, the side walls 12a flex inwardly and as the pressure continues to increase, the side walls 12a continue to approach each other. When the pressure has increased beyond the point where the side walls would come together, the pressure will tend to collapse the edges 12b. Once the yield point of the material at the bend 12b has been exceeded, fractures occur along the edges and the tube will not spring back to the original shape shown in FIG. 3.

According to an important feature of this invention, the depth of submergence of tube 12 can be materially increased without damage to the tube. Into the tube 12 is telescoped the shaped core 14 of rubber-like material.

Although semi-soft rubber and many plastics may have little strength in tension, they do have considerable strength in compression. The core 14 is of such shape and bulk as to lend substantial support for the edge portions 12b of the metal or fiberglass tube 12 when the sidewalls come into pressure contact. The cross sectional shape in FIGS. 2, 3 and 4 approximates a shallow figure eight the diameter of the two rims being sized to slip easily into the tube. When a molded or extruded core of rubber or similar substance is placed inside the tube 12 as shown, the tube will press against the core and no foci of stress can be created in the tube 12 since the tube wells are under compressional stress only, which stress is distributed evenly throughout the tube. Self supporting core within the tube 12 have the advantage over liquid fillers in that the rubber will not slosh or shift from place to place within the tube as would liquid.

The tubes must be hermetically sealed. The ends may be pinched together, as stated, and closed with a suitable adhesive, or a plug could be glued in place in each tube end. Conveniently, the core members can be cut to the length of the tubes and an adhesive connection made at the ends. As suggested in FIG. 2, the core may be cast with flattened end portions to facilitate the end seals.

Alternatively, the core may comprise of metal plate 14a embedded along the edges in rounded beads 14b, as shown in FIGS. 5 and 6. The dimensions of the plate and heads are chosen to telescope easily into the tube and to support the tube, without breaking stresses, when the tube is completely collapsed.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that the in- 3 vention may be practiced otherwise than as specifically described.

What is claimed is: 1. In a transducer adapted for deep-submergence operation, pressure release means comprising:

an elongated compliant tube, said tube being closed at each end, being flattened in cross section, and being yieldably collapsible under external pressure, and an elongated core member within said tube for supporting the walls of said tube and for limiting the degree of collapse to prevent fracture of the Walls of said tube, said core member being figure-8 in cross section with the thin center portion of the member disposed opposite the flattened wall portions of said tube and the rounded edge portions of the core member substantially conforming in size and shape to the curved edge portions of said tube. 2. In a transducer, pressure release means comprising, a plurality of elongated tubes, said plurality of tubes being arranged side-by-side in a bundle, a header at each end of said bundle and attached to the end of each tube,

each tube being closed at each end, and being fiattened in cross section and being yieldably collapsible under external pressure, and

an elongated core member Within each tube for supporting the Walls of the tube and for limiting the degree of collapse to prevent fracture of the walls of the tube. 10 References Cited UNITED STATES PATENTS 3,002,179 9/1961 Kuester 3408 3,021,504 2/1962 Toulis 340-8 X 15 3,176,787 4/1965 Roever 181-.5 3,264,605 8/1966 Vincent 3408 3,320,579 5/1967 Abbott 340-8 RODNEY D. BENNETT, JR., Primary Examiner 20 B. L. RIBANDO, Assistant Examiner 

